Transbilayer Movement and Distribution of Cholesterol

Membrane properties of hydroxycholesterols related to the brain cholesterol metabolism

“…Nevertheless, the import and export of cholesterol is rather slow [ 34 ], wherefore membrane proteins have been proposed to facilitate these processes. One putative function of those proteins could be to relieve the presentation of cholesterol molecules on the membrane surface for a better binding to extracellular acceptors (see [ 35 ]). It can be hypothesized, that the lower membrane embedding of hydroxycholesterols facilitates their membrane incorporation and/or release.…”

“…With regard to the transbilayer mobility of sterols, it is generally assumed that cholesterol traverses the bilayer very rapidly by passive diffusion, although at certain conditions, e.g., special membrane compositions, its transbilayer movement could be compounded (see [ 35 ]). For hydroxycholesterols, the transbilayer movement has not been investigated so far.…”

Interaction of fluorescent phospholipids with cyclodextrins

“…For long chain (endogenous) phospholipids such a slipping mobility perpendicular to the membrane surface is energetically unfavorable and should only occur with a very low probability. For cholesterol, its comparatively large slipping mobility resulting in a protrusion out of the membrane surface has been proposed to explain its release from membranes onto ßCDs (Müller et al, 2011;Milles et al, 2013). With regard to the second point, phospholipids are anchored within the membrane on the basis of the hydrophobic effect with some dependence on interactions between the head groups and van der Waals interactions within the bilayer chain region influencing their susceptibility towards extravesicular or extracellular acceptors.…”

“…Modifications of CDs at the hydroxyl groups of glucose such as methylations or hydroxypropylations modulate the affinity of lipids for CDs (Szente and Szejtli, 1999;Uekama, 2004). The high specificity of ßCD and its derivatives for sterols has been applied to characterize the physiological role of this lipid e.g., to manipulate the sterol content of membranes by extracting or incorporating cholesterol from/into membranes, to measure the cellular sterol dynamics and, to incorporate labeled sterol analogs into membranes (Müller and Herrmann, 2002;Wüstner, 2007;Zidovetzki and Levitan, 2007;Müller et al, 2011;Milles et al, 2013).…”